Research On The Effect Of Synchronous Condenser Connected To HVDC Receiver And The Optimization Of Excitation Control

The development and application of HVDC transmission has greatly relieved the pressure of power shortage in the receiving end load center.At the same time,the large-scale feeding of DC also brings great risks to the security and stability of the receiving-end grid.Aiming at the problem of the insufficient dynamic reactive power reserve in the receiving-end grid,"large DC power transmission and strong reactive power support" is objectively required.The Large capacity synchronous condenser has become a hot research topic once again because of its excellent transient reactive power support ability.Firstly,the working principle of synchronous condenser is analyzed.Then based on the knowledge of electrical machinery,its mathematical model and the expressions of reactive power output characteristics under different time scales are established.At the same time,the operation mechanism of HVDC transmission system and the reactive power characteristics of the converter station are also studied.The above content lays the foundation for subsequent research.Secondly,the simulation model of the synchronous condenser connected to the HVDC receiving-end system is built on the PSCAD/EMTDC platform.Then the dynamic response of the system with or without the synchronous condenser is compared by the simulation under three different working conditions:AC shortcircuit fault,DC short-circuit fault and sudden increase in reactive load.The results show that the synchronous condenser can effectively enhance the anti-interference ability of the receiver system,but there is no significant improvement in the DC transmission power under the DC short-circuit fault.According to the close correlation between reactive power and voltage,the commutation bus voltage is selected as the key observation object.Then the voltage support effect of the synchronous condenser under different fault levels,different AC system strengths and different access capacities is further studied,which provides a certain reference for the configuration of the synchronous condenser.Finally,in view of the overshoot and fluctuation problems caused by the conventional PI control of the synchronous condenser during the fault recovery process,this thesis combines the grey prediction control with the conventional PI control,and designs the grey prediction PI excitation control system of the synchronous condenser and then simulates it under different fault conditions.Compared with the simulation results of the synchronous condenser transmission system with conventional PI control,the results show that the designed system based on the improved excitation control has better dynamic response performance and reactive power compensation effect,which effectively alleviates the overshoot and fluctuation of the system.